ORGANIZATION OF THE OUTER LAYERS OF THE CELL-ENVELOPE OF CORYNEBACTERIUM-GLUTAMICUM - A COMBINED FREEZE-ETCH ELECTRON-MICROSCOPY AND BIOCHEMICAL-STUDY

The cell surface of Corynebacterium glutamicum grown on solid medium w as totally covered with a highly ordered, hexagonal surface layer. Als o, freeze-fracture revealed two fracture surfaces which were totally c overed with ordered arrays displaying an hexagonal arrangement and the same unit cell dimension as the surface layer. The ordered arrays on the concave fracture surface, closest to the cell surface, were due to the presence of particles while those on the convex fracture surface were their imprints. The same cells grown on liquid medium displayed a cell surface and fracture surfaces only partially covered with ordere d arrays. In this case, the ordered regions had the same relative posi tion on the cell surface and on the fracture surfaces. All ordered arr ays were totally absent in a mutant for cspB, the gene encoding PS2, o ne of the two major cell wall proteins. Treatment of the cells with pr oteinase K caused the gradual alteration of PS2 into a slightly lower molecular mass form. This was accompanied by a concomitant disappearan ce of the ordered fracture surfaces followed by the detachment of the ordered surface layer from the cell as large ordered patches displayin g the same lattice symmetry and dimension as those of the surface laye r. The ordered patches were isolated. They contained the totality of P S2 initially associated with the cell. We conclude that the highly ord ered surface layer of the intact cell was composed of PS2 interacting strongly with some cell wall material leading to its organization. Thi s organized cell wall material produced the ordered fracture surfaces. We show that in the absence of intact PS2 protein on the cell wall, t he same cell wall material was not organized and formed a structureles s smooth layer.